JPH04273953A - Liquiefied refrigerating apparatus - Google Patents

Abstract

PURPOSE:To permit load proportion R/L to be selected widely, while maintaining the total amount of liquefaction and cooling loads and the operational efficiency at a high level. CONSTITUTION:Liquefied refrigerating apparatus which comprises a plurality of intermediate heat exchangers HEX3-HEX5, each composed of two heat exchangers HEX3a and HEX3b almost equal to each other in heat transfer area; and a low temperature heat exchanger HEX1 composed of a primary heat exchanger HEX1a and more than one secondary heat exchangers HEX1b and HEX1c, whereby the heat-exchanging action is made switchable between the intermediate heat exchangers and the low temperature heat exchanger in use.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for liquefying and freezing gases such as helium and hydrogen.

0002

2. Description of the Related Art Conventionally, devices have been provided that cool a gas such as helium, liquefy a part of it, and use the remaining part for freezing (Japanese Patent Laid-Open No. 2-183788, etc.).

FIG. 6 shows an example of such a device. In the figure, C is a compressor, HEX1 to HEX6 are six stages of heat exchangers connected in series, and the room temperature and high pressure gas compressed by the compressor C is heat exchanged in each heat exchanger HEX6 to HEX1. JT valve (Joule-Thomson valve) 1
Sent to 0. The JT valve 10 expands the gas, and a portion of the gas is liquefied and extracted, and the remainder is returned to the compressor C as a low-pressure gas after contributing to refrigeration through the heat exchangers HEX1 to HEX6.

Further, the high pressure line and the low pressure line are bypassed by a passage 20, and a turbine supply valve 18 and expansion turbines T1 and T2 for generating cold are arranged in series in this bypass passage 20. The amount of cold generated changes depending on the degree of opening.

Generally, in such a helium liquefaction refrigeration system, the planning point (design The value that is used most frequently is selected as the point), and the gas pressure,
Temperature, flow rate, turbine specifications, and each heat exchanger HEX
1 to HEX6 are selected.

Specifically, the temperature level (average value of inlet temperature and outlet temperature) on the high pressure side of the heat exchanger is t1, and the temperature difference between the high pressure side and the low pressure side of the heat exchanger (for example, the temperature level of the heat exchanger in FIG. In HEX6, if the temperature difference t1-t2) between the temperature t1 on the high pressure side and the temperature t2 on the low pressure side is Δt, then the above temperature level t
It is conventionally known that liquefaction freezing can theoretically be performed most efficiently by setting each specification so as to obtain a temperature difference Δt as shown in Table 1 below (low temperature Engineering Handbook (VEREIN DEU)
(Author: TSCHERINGENIEURE, Published by Uchida Rokakupa Shinsha), see page 20).

[0007]

[Table 1]

[0008] Therefore, when designing an actual device,
Each specification such as the substantial heat transfer area of each heat exchanger is set so that the temperature difference in each heat exchanger corresponds to the value in Table 1 above when operating at a desired load ratio R/L.

[0009]

[Problem to be Solved by the Invention] In the device designed as described above, liquefaction and freezing can be performed efficiently by operating at the load ratio R/L at the planning point, but other than that. When trying to obtain a load ratio R/L of be. However,
Such operations are nothing but changes in the mass flow rate of circulating helium and the amount of cooling produced by the turbine, and the more such changes are made, the greater the actual temperature difference Δt in each heat exchanger will be as shown in Table 1 above. If the value deviates from the indicated value, the efficiency will decrease significantly.

Furthermore, the above device has the following problems. In the same device, if the optimum load ratio R/L is set to a relatively small value (for example, point G1 in FIG. 7), by throttling the JT valve 10 from this point, the temperature difference Δt1 of the heat exchanger increases. Accordingly, the load ratio R
Point G where /L is 0 (that is, refrigeration load R is 0)
2, but conversely, the above optimal point G1
When the JT valve 10 is opened to lower the load ratio R/L, for example, the temperature difference Δt in the heat exchanger HEX1 is 0,
Or it reverses and becomes negative (i.e. the temperature t2 on the low pressure side
becomes lower than the temperature t1 on the high-pressure side), and large temperature fluctuations occur within the device, resulting in the inconvenience that stable operation is no longer possible. That is, in this device, if the design point is set at the above point G1, the load ratio R/L cannot shift toward infinity (that is, the liquefaction load L is 0) even if the JT valve 10 etc. is operated. , operable load ratio R/L
has the disadvantage that it is limited to an extremely narrow range.

On the other hand, if the optimum point is set in advance at the point where the liquefaction load L is 0, as shown at point H1 in the figure, then the throttle valve 1
By adjusting 0, etc., the operating state can be changed from point H1 where R/L is infinite to point H2 where R/L is 0. However, when the optimum point is selected as point H1 in this way, as is clear from FIG.
There is a disadvantage that +L is significantly reduced.

In view of these circumstances, the present invention provides a liquefaction refrigeration system that allows the load ratio R/L to be selected from a wide range while maintaining the total amount R+L of the liquefaction load L and the refrigeration load R and the operating efficiency at a high level. The purpose is to

[0013]

[Means for Solving the Problems] The present invention includes a compression means for compressing a gas to be treated, a plurality of heat exchangers arranged in series, and a compressor for expanding the high-pressure gas that has passed through these heat exchangers. An expansion liquefaction means for liquefying at least a part of the gas, and an expansion turbine for expanding a part of the gas on the high-pressure side to generate refrigeration and sending it to the low-pressure side, the high-pressure gas compressed by the compression means The gas is cooled by heat exchange in a plurality of heat exchangers, a desired proportion of the gas is liquefied by expansion by the expansion and liquefaction means, the remaining gas is contributed to refrigeration, and is passed through the heat exchanger in a low pressure state to liquefy the gas by the compression means. In the liquefaction refrigeration system configured to return to Consisting of two heat exchangers arranged in parallel with each other and having substantially equal heat transfer areas, the low-temperature heat exchanger closest to the expansion and liquefaction means is a basic heat exchanger, and this basic heat exchanger 0.5~ of the same basic heat exchanger.
It is composed of one or more sub-heat exchangers having a substantial heat transfer area of 1.0 times, and is equipped with a switching means for switching the heat exchanger used in the intermediate heat exchanger and the low-temperature heat exchanger. Yes (Claim 1). Here, "three intermediate heat exchangers sandwiching the expansion turbine" refers to the heat exchanger closest to the inlet side of the expansion turbine, the heat exchanger closest to the outlet side of the expansion turbine, and the heat exchanger closest to the outlet side of the expansion turbine. A heat exchanger sandwiched between heat exchangers.

Further, in the case of an apparatus in which a second expansion turbine is provided in the high pressure line, the two heat exchangers sandwiching the second expansion turbine are used as low temperature heat exchangers, and the low temperature heat exchanger is used as a low temperature heat exchanger. The heat exchanger is composed of a basic heat exchanger and one or more auxiliary heat exchangers arranged in parallel with this basic heat exchanger and having an effective heat transfer area of 0.5 to 1.0 times that of the basic heat exchanger. (Claim 2).

[0015] Furthermore, in each of the above devices, the intermediate heat exchanger and the low-temperature heat exchanger are configured so that heat conduction occurs between the heat exchangers constituting these devices, which makes it more preferable (as claimed in the claims). Items 3 and 4).

[0016]

[Operation] According to the apparatus according to the above claims 1 and 2, in the intermediate heat exchanger and the low temperature heat exchanger, the desired load ratio R
By switching the heat exchanger used so as to obtain the optimum effective heat transfer area for operation at R/L, stable liquefaction and freezing can be performed at various load ratios R/L. The principle and specific operation switching will be explained in detail later in the section of Examples.

Furthermore, according to the apparatus according to claim 3, even when one heat exchanger is used for operation, heat transfer from this heat exchanger also causes the other heat exchanger that is not in operation to be heated. Since it is cooled, almost no thermal shock occurs even when switching from this state to a state where the other heat exchanger is used. This also applies to the device according to claim 4.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flowchart of a two-turbine cycle type helium liquefaction refrigeration system according to a first embodiment of the present invention. Note that the entire device is housed in a cold box (not shown).

This device includes a compressor (compression means) C, a total of six stages of heat exchanger groups HEX1 to HEX6, and J arranged in series.
It includes a T valve (liquefaction expansion means) 10 and two cold generation expansion turbines T1 and T2 arranged in series with each other. Furthermore, as a feature, among the above heat exchanger group, J
The heat exchangers HEX2 and HEX6 corresponding to the second stage and the sixth stage counting from the T-valve 10 are composed of a single heat exchanger HEX2 and HEX6 as in the past, but 3 to 5
Stage heat exchanger (corresponds to intermediate heat exchanger in the present invention) HE
X3 to HEX5 are 2 with mutually equal substantial heat transfer areas.
2 heat exchangers (HEX3a, HEX3b), (HEX4
a, HEX4b) and (HEX5a, HEX5b), respectively. Also, the first stage heat exchanger closest to the JT valve 10 (corresponds to a low temperature heat exchanger in the present invention)
HEX1 is 1.0 times and 0.5 times larger than the basic heat exchanger HEX1a and this basic heat exchanger HEX1a, respectively.
Sub-heat exchanger HEX1b, HEX with twice the actual heat transfer area
1c.

[0020] The "substantive heat transfer area of the heat exchanger" herein is expressed by the product UA of the overall heat transfer coefficient U and the total heat transfer area A of the heat exchanger. Moreover, the specific setting procedure of the substantial heat transfer area of each heat exchanger will be explained in detail later.

[0021] Heat exchanger HEX1 divided into two or more parts,
In HEX3, HEX4, and HEX5, the divided heat exchangers (for example, heat exchangers HEX5) may be completely independent, but, for example, as in the heat exchanger HEX5 shown in FIG. Exchanger HEX5a, HEX5b
are integrally molded, and both heat exchangers HEX5a and H
A heat conductive part 5c made of a metal partition wall or the like is provided between EX5b so that heat exchange is performed individually in each heat exchanger HEX5a and HEX5b, and both heat exchangers H
If the structure is such that heat conduction occurs between EX5a and HEX5b, better effects can be obtained as described later.

In such an apparatus, the high-pressure helium gas compressed by the compressor C passes through the sixth stage heat exchanger HEX6 for pre-cooling into which liquid nitrogen is introduced, and then passes through the switching valve (passage switching means) 16. is opened, the flow is divided into passage 12 and passage 14, and one is connected to heat exchangers HEX5a, HEX4a, H
EX3a, and the other is heat exchanger HEX5b, HEX
Pass through 4b and HEX3b. On the other hand, the switching valve 16
When the HEX is closed, all the gas flows through one heat exchanger HEX.
5a, HEX4a, and HEX3a only.

Furthermore, a portion of the gas flowing through each passage 12, 14 enters the bypass passage 20, passes through expansion turbines T1, T2 provided in this passage 20, and is sent to the low pressure line side, which will be described later. The necessary chilling occurs. This change in the amount of cold generation, that is, the change in the turbine flow rate, is performed by adjusting the opening degree of the turbine supply valve 18.

The remaining gas flowing through the passages 12 and 14 joins with each other, passes through the second stage heat exchanger HEX2, and then passes through the passages 22a, 22b, and 22c to the first stage heat exchanger (referred to in the present invention). Compatible with low temperature heat exchanger) HEX1
will be introduced in

The gas that has passed through the first stage heat exchanger HEX1 is in a low temperature state due to the heat exchange in the heat exchanger group described above, and in this state is introduced into the JT valve 10, where it is expanded. A part of the liquid is liquefied and extracted, and the remaining part passes through the passage 24 and contributes to freezing, and the remaining part passes through the passage 26a,
It is sent back to the first stage heat exchanger through 26b and 26c.

Here, as described above, each heat exchanger HEX1
The high pressure side passages 22a to 22c and the low pressure side passages 26a to 26c passing through a to 1c are provided with switching valves (passage switching means) 28 to 33, respectively, and by opening and closing these,
The heat exchanger used in the first stage heat exchanger HEX1 can be switched.

After passing through the second stage heat exchanger HEX2, the low pressure gas led out from the first stage heat exchanger HEX1 passes through the passages 35 and 36 with the switching valve (passage switching means) 38 open. One heat exchanger group HEX3a, H
EX4a, HEX5a or the other heat exchanger group HEX
After passing through HEX 3b, HEX 4b, and HEX 5b, it is returned to the compressor C. On the other hand, when the switching valve 38 is closed, all the gas passes only through the passage 35, that is, one heat exchanger group HEX3a, HEX4a, HEX5a
is returned to the compressor C through the

To summarize the above, in this device, among the six stages of heat exchangers, a three stage heat exchanger (with a temperature level below 77°C and sandwiching the expansion turbine T1 closest to 77°C) is used.
In other words, the heat exchanger HEX5 closest to the inlet side of the expansion turbine T1 and the heat exchanger HEX5 closest to the outlet side of the expansion turbine T1
3, and the heat exchanger HE sandwiched between both heat exchangers HEX5 and 3.
The first stage heat exchanger (low temperature heat exchanger according to the present invention) HEX1, which is closest to the JT valve 10, is the basic heat exchanger HEX1a. and auxiliary heat exchangers HEX1b, 1c, and switching valves 16, 3.
By opening and closing the switching valves 8 and 28 to 33, the heat exchangers used in the intermediate heat exchangers HEX3 to HEX5 and the low temperature heat exchanger HEX1 can be changed.

Next, a method of performing liquefaction freezing with high efficiency using this apparatus and its fundamental principle will be explained.

In FIG. 2, point E-2 shown in the figure is selected as the optimal point (that is, the most suitable point for operation), and the heat exchanger temperature differences Δt23, Δt45, Δt1819 are set to optimal values at this point. The solid line EL1 shows the changes in loads L, R and Carnot efficiency η when only the temperature difference Δt23 is expanded from this point, and the temperature difference Δt1 from the above point E-2 is
The broken line EL2 shows the changes in the loads L and R and the Carnot efficiency η when only 819 is expanded.

Note that Δt23 is the temperature difference between points P2 and P3 in FIG. 1, and Δt45 is the temperature difference between points P2 and P3 in FIG.
The temperature difference between points P18 and P5 and Δt1819 mean the temperature difference between points P18 and P19 in FIG. 1, respectively.

As shown in FIG. 2, the point E-2
If a device is designed by selecting the optimum point, and if only the temperature differences Δt23 and Δt1819 can be individually expanded from the above point E-2 in this device, stable and relatively highly efficient operation can be ensured. , load ratio R/L is 0
This means that you can choose from an extremely wide range from ∞ to ∞.

Table 2 below shows the above points E-1 and E-2.
, E-3, E-4, the results of calculating the effective heat transfer area of the heat exchanger suitable for performing liquefaction and freezing with the temperature difference Δt of each heat exchanger above are expressed as a ratio with point E-2. It is something. In addition, in the same table, UAi is the i-th heat exchanger HEX.
i means the optimal real heat transfer area, and η means the thermodynamic work efficiency (Carnot efficiency).

[0034]

[Table 2]

As shown in this table, the second stage heat exchanger HEX2 can be operated satisfactorily with substantially the same heat transfer area at any point, regardless of the load ratio R/L. On the other hand, for the three heat exchangers HEX3 to HEX5 that sandwich the expansion turbine T1, the optimum effective heat transfer area at point E-2 is smaller than that at point E-2.
3. The optimum effective heat transfer area in E-4 is about half. In addition, the first stage heat exchanger (low temperature heat exchanger) HEX1
Regarding, compared to the optimal effective heat transfer area at the optimal point E-2, the optimal effective heat transfer areas at other points E-1, E-3, and E-4 are about 0.5 times and about 1.5 times, respectively. It is approximately 2.5 times as large.

To summarize the above, when the optimum point E-2 is used as a reference, at the point E-1, the first stage heat exchanger HEX1
At point E-3, the effective heat transfer area of the first stage heat exchanger HEX1 is approximately 1.5 times as large as that of the third to fifth stage heat exchangers HEX3 to HEX5. The heat transfer area is increased by approximately 0.5 times, and at point E-4, the effective heat transfer area HEX1 of the first stage heat exchanger is increased approximately 2.5 times, and the heat transfer area of the third to fifth stage heat exchangers HEX3 to HEX5 is By increasing the actual heat transfer area by approximately 0.5 times, R/L can be increased from 0 to ∞
This means that stable and highly efficient operation can be performed over a wide range of areas. Note that the optimum effective heat transfer area of the sixth stage heat exchanger HEX6 for pre-cooling is also reduced at points E-3 and E-4 compared to the optimum point E-2; HEX6
Since the temperature level at can be changed by adjusting the amount of liquid nitrogen introduced, there is no need to particularly change the heat transfer area.

Considering the results explained above, FIG.
In the apparatus shown in , it is possible to realize good operation at each point E-1 to E-4 by setting the heat transfer area and switching the passages as described below.

[0038] When designing, each heat exchanger H constituting the 3rd to 5th stage heat exchangers HEX3 to HEX5
The substantial heat transfer areas of EX3a to HEX5a and HEX3b to HEX5b are each set to half the optimum substantial heat transfer areas of the third to fifth stage heat exchangers HEX3 to HEX5 at the optimum point E-2. Furthermore, the first stage heat exchanger HEX
The substantial heat transfer area of the basic heat exchanger HEX1a and one of the auxiliary heat exchangers 1b constituting 1 is set equal to the optimum substantial heat transfer area of the first stage heat exchanger HEX1 at the optimum point E-2, and , the substantial heat transfer area of the other sub-heat exchanger 1c is set to half the optimum substantial heat transfer area of the basic heat exchanger HEX1a. In addition, the 2nd and 6th stage heat exchanger HEX
The effective heat transfer areas 2 and 6 are set equal to the optimum effective heat transfer area at the optimum point E-2, as in the conventional case.

■ In a device designed as described above, when operating at the optimum point E-2, the switching valve 28
, 29 and the switching valves 16, 38 are opened, and the switching valve 3 is opened.
By closing 0 to 33, the 3rd to 5th stage heat exchanger HEX
3 to HEX5, heat exchangers HEX3a, HEX4a, H
EX5a and heat exchanger HEX3b, HEX4b, HE
The first stage heat exchanger HEX1 is operated using only the basic heat exchanger HEX1a.

■ When operating at point E-1, the switching valves 32, 33 and 16, 38 are opened, and the switching valves 28, 29, 32, 33 are closed.
~In the 5th stage heat exchanger HEX3~HEX5, the heat exchanger HE
X3a, HEX4a, HEX5a and heat exchanger HEX
3b, HEX4b, and HEX5b, and the first stage heat exchanger HEX1 is operated using only the basic heat exchanger HEX1a. As a result, the substantial heat transfer area of the first stage heat exchanger HEX1 becomes half of the substantial heat transfer area at the point E-2.

■ When operating at point E-3, open the switching valves 28, 29, 32, and 33, and open the switching valve 30.
, 31 and the switching valves 16, 38.
~In the 5th stage heat exchanger, heat exchangers HEX3a and HEX4a
, HEX5a only, and the first stage heat exchanger HEX1 is operated using the basic heat exchanger HEX1a and the auxiliary heat exchanger HEX1c. As a result, the 3rd to 5th stage heat exchanger H
The actual heat transfer area of EX3 to HEX5 is half of the actual heat transfer area at the above point E-2, and the first stage heat exchanger HEX1
The substantial heat transfer area is 1.5 times the substantial heat transfer area at the above point E-2.

■ When operating at point E-4, all switching valves 28 to 33 are opened and switching valves 16 and 38 are closed, and in the third to fifth stage heat exchangers, heat exchangers 3a, 4a, and 5 are closed.
In the first stage heat exchanger, all the heat exchangers, i.e., the basic heat exchanger 1a and the auxiliary heat exchanger HEX1b, are used.
Perform operation using 1c. As a result, the actual heat transfer area of the third to fifth stage heat exchangers HEX3 to HEX5 is the point E-2 above.
is half of the actual heat transfer area in the first stage heat exchanger H.
The substantial heat transfer area of EX1 is 2.5 times the substantial heat transfer area at the above point E-2.

By carrying out the above operations (1) to (2), it is possible to realize good operation at each point E-1 to E-4 with a substantial heat transfer area suitable for that point. More specifically, for example, if you want to shift the operating state from the above optimum point E-2 to point E-3, perform the operation ① above to move to the safe side (that is, the side where the heat exchanger temperature difference Δt1819 increases). The operating state may be changed by changing the actual heat transfer area of the heat exchanger and then making adjustments such as increasing the opening degree of the JT valve 10. Here, if an attempt is made to open the JT valve 10 and increase the load ratio R/L while the heat transfer area remains unchanged as in the conventional device, the heat exchanger temperature difference Δt23 will be 0 or reversed and the operating state will become unstable. However, by changing the heat transfer area to a safe side in advance as in the device of the present invention, it is possible to change the load ratio R/L while maintaining stability and high efficiency. Become.

In addition, when moving from the optimum point E-2 to the point E-1, even if the actual heat transfer area of the first stage heat exchanger HEX1 is not halved by performing the operation (2) above, the JT Valve 1
Although it is possible to make the transition by simply performing a throttle operation of 0, if the effective heat transfer area is halved as described above, the effective heat transfer area will approach the optimum value, and the helium liquefaction efficiency will be further improved. becomes.

As a comparative example, FIG. 2 shows a point F- where the load ratio R/L is infinite (that is, the liquefaction load L is 0).
1 is set as the optimal point, and from this optimal point F-1, only the heat exchanger temperature difference Δt23 is expanded to reach a point F- where R/L is 0.
3 is shown by the solid line FL, and Table 3 below shows the optimum substantial heat transfer area of each heat exchanger at both points F-1 and F-3.

[0046]

[Table 3]

[0047] In Table 3, the values of the actual heat transfer area and compressor power that are not in parentheses are at the optimum point E-2.
The value in parentheses is the ratio to the value at point F-1.

As is clear from the solid line FL, solid line EL1, and broken line EL2 in FIG. 2, according to the apparatus of the present invention, the load ratio R/L can be shifted from about 0 to ∞ even at various optimal points. However, in order to ensure a large total amount R+L of the refrigeration load R and liquefaction load L,
The optimum point is determined by setting the load ratio R/L to a value as small as possible below 1 (
For example, it is desirable to set it to E-2). In other words, the closer the optimum point is to the point where the load ratio R/L is ∞, the smaller the difference from the conventional device in the total load amount R+L becomes.

In addition, in the above-mentioned apparatus, as shown in FIG. 3, both heat exchangers HEX5a and HEX5b
If heat conduction is performed between the two heat exchangers, for example, while only one heat exchanger HEX5a is operating, heat conduction from this heat exchanger HEX5a will cause the other heat exchanger H
Since EX5b is also cooled, thermal shock is less likely to occur even when switching to a state in which both heat exchangers HEX5a and HEX5b are operated next, making it possible to smoothly switch the operating state. Furthermore, both heat exchangers 5a and 5b
By integrating the two, there is an advantage that the device can also be made smaller.

Next, a second embodiment will be explained based on FIGS. 4 and 5.

[0051] Here, a liquefaction refrigeration system with 5 turbine cycles and 10 stages of heat exchangers is shown.

In the figure, C1 and C2 are two-stage compressors arranged in series. In addition, the 7th to 10th stage heat exchanger HE
X7 to HEX10 are heat exchangers for pre-cooling, through which liquid nitrogen for pre-cooling is passed, and a passage 40 in which expansion turbines T3 and T4 for generating cold are arranged in series is passed,
A turbine supply valve 42 is provided in this passage 40 .

As in the first embodiment, three heat exchangers HEX4 to HE sandwich an expansion turbine T1 having a temperature level lower than the boiling point of nitrogen and closest to this boiling point.
X6 are heat exchangers HEX4a, HEX4b, heat exchangers HEX5a, and HEX5a, which have substantially equal heat transfer areas, respectively.
It is composed of HEX5b and heat exchangers HEX6a and HEX6b.

On the other hand, an expansion turbine T5 for cold generation is provided in the high pressure line between the first stage heat exchanger HEX1 and the second stage heat exchanger HEX2, and this expansion turbine T5 is bypassed. A turbine flow rate control valve 54 is provided in the passage 52 where the turbine flow rate is controlled. Two heat exchangers HEX1 and HEX2 sandwich this expansion turbine T5,
Each is composed of basic heat exchangers HEX1a, HEX2a and auxiliary heat exchangers HEX1b, HEX2b. In addition, with the division of the second stage heat exchanger HEX2,
The high-pressure line and low-pressure line in this part also branch into two passages 44, 46 and 56, 58, respectively, with passages 44, 56 in one heat exchanger HEX2a and passages in the other heat exchanger HEX2b. 46 and 58 are passing through respectively. Further, each passage 44, 46, 56, 58 is provided with a switching valve 48, 50, 60, 62.

Next, a method for operating this device with high efficiency and its underlying principle will be explained.

FIG. 5 shows points D-2 and B-1 shown in the figure.
, C-1 are respectively the optimal points, and the heat exchanger temperature differences Δt23, Δt45, Δt1819 are set to the optimal values at these points, and only the temperature difference Δt45 is expanded from each point.Load L, R and Carnot efficiency Changes in η are shown by solid lines DL1, BL1, and CL1, respectively, and changes in loads L and R and Carnot efficiency η when only the temperature difference Δt1819 is expanded from each point above are shown by broken lines DL2 and BL2, respectively.
, CL2. In addition, Tables 4 to 6 shown below calculate the actual heat transfer area of the heat exchanger suitable for performing liquefaction and freezing with the temperature difference Δt of each heat exchanger at each point shown in Figure 5 above. The results are shown as points D-2,
It is expressed as a ratio between B-1 and C-1.

[0057]

[Table 4]

[0058]

[Table 5]

[0059]

[Table 6]

[0060] In these tables and FIG.
3, T4 stop" and "T5 stop" respectively mean an operation in which expansion turbines T3 and T4 are stopped, and an operation in which expansion turbine T4 is stopped.
5 is stopped.

As shown in these tables, the heat exchangers HEX2 in the 7th to 10th stages and the 3rd stage can be operated satisfactorily with substantially the same heat transfer area at all points. On the other hand, similarly to the embodiment, three heat exchangers (intermediate heat exchangers) H sandwiching the expansion turbine T1.
For EX4 to HEX6, the optimal points D-2, B-1,
Compared to the optimum effective heat transfer area at C-1, points D-3,
The optimum substantial heat transfer area in B-2 and C-2 is about half. In addition, 1st and 2nd stage heat exchangers (low temperature heat exchangers)
For HEX1 and HEX2, optimal points D-2 and B-1
, C-1, point D-1,
The optimum substantial heat transfer area at points B-0 and C-0 is approximately 0.5 times, and the optimum substantial heat transfer area at points D-3, B-2, and C-2 is approximately 1.5 times.

To summarize the above, optimal points D-2, B-1
, C-1 as a reference, each point D-1, B-
For 0, C-0, 1st and 2nd stage heat exchangers HEX1, 2
The effective heat transfer area of is approximately halved, and each point D-3, B-2, C
-2, the actual heat transfer area of the first stage heat exchanger HEX1 is approximately 1.5 times, and the third to fifth stage heat exchanger HEX1 is
By increasing the effective heat transfer area of 3 to HEX5 by approximately 0.5 times, stable and highly efficient operation can be performed in a wide range of R/L from 0 to ∞.

As a comparative example, FIG. 5 shows the transition of R/L and Carnot efficiency η when the operating conditions are changed using point A, where the load ratio R/L=∞, is the optimum point. Table 6 shows the optimum effective heat transfer coefficient at the above point A.

According to the results described above, in the apparatus shown in FIG. 4, good operation can be achieved in each respect by setting the heat transfer area and switching the passages as described below.

■ When designing, each heat exchanger H constituting the 4th to 6th stage heat exchangers HEX4 to HEX6
The effective heat transfer areas of EX4a to HEX6a and HEX4b to HEX6b are set at each optimum point D-2, B-1,
4th to 6th stage heat exchangers HEX4 to HEX6 in C-1
set to half of the optimum effective heat transfer area, and 1,2
Basic heat exchanger HE that constitutes stage heat exchangers HEX1 and 2
The effective heat transfer areas of X1a and HEX2a are set to half the optimum effective heat transfer areas of the first and second stage heat exchangers HEX1 and HEX2 at each of the above optimum points, and the sub heat exchangers HEX1b and H
The effective heat transfer area of EX2b is set to 1, 2 at the above optimum point.
It is set equal to the optimum effective heat transfer area of the stage heat exchangers HEX1 and HEX2. Further, the substantial heat transfer areas of the other heat exchangers are set equal to the optimum substantial heat transfer areas at each optimum point, as in the conventional case.

■ When operating at the optimum points D-2, B-1, C-1, the switching valves 28, 29 and the switching valves 16, 3
8, and the switching valves 48 and 60, and the switching valve 3
By closing 0 to 33 and the switching valves 50 and 62,
In the 4th to 6th stage heat exchangers HEX4 to HEX6, heat exchanger H
EX4a, HEX5a, HEX6a and heat exchanger HE
Using both X4b, HEX5b, HEX6b, 1,2
In the stage heat exchangers HEX1 and 2, the basic heat exchanger HEX1a
, so that operation is performed using only HEX2a.

■ When operating at points D-1, B-0, C-0, switching valves 30, 31, switching valves 16, 38,
and the switching valves 50, 62 are opened and the switching valves 28, 2 are opened.
9, 32, 33 and switching valves 48, 60, the fourth to sixth stage heat exchangers HEX4 to HEX6 use both heat exchangers HEX4a, HEX5a, HEX6a and heat exchangers HEX4b, HEX5b, HEX6b,
In the 1st and 2nd stage heat exchanger HEX1, the auxiliary heat exchanger HEX1b
, perform operation using only HEX2b. This results in 1
, the substantial heat transfer area of the second-stage heat exchangers HEX1, HEX2 is half of the substantial heat transfer area at the optimum points D-2, B-1, C-1.

■ When operating at points D-3, B-2, and C-2, switching valves 28 to 31, switching valves 48, 60,
and the switching valves 50, 62 are opened and the switching valves 16, 3 are opened.
8 and switching valves 32 and 33, 4 to 6
In the stage heat exchanger, heat exchangers HEX4a, HEX5a, H
Using only EX6a, 1st and 2nd stage heat exchangers HEX1,H
In EX2, operation is performed using both the basic heat exchangers HEX1a and HEX2a and the auxiliary heat exchangers HEX1b and 2b. As a result, the effective heat transfer area of the 4th to 6th stage heat exchangers HEX4 to HEX6 becomes half of the effective heat transfer area at the above optimal points D-2, B-1, and C-1, and the 1st and 2nd stage heat exchangers Vessel H
The actual heat transfer area of EX1 and HEX2 is the optimum point D-2,
This is 1.5 times the substantial heat transfer area in B-1 and C-1.

By carrying out the above operations (1) to (2), it is possible to realize good operation at each point with a substantial heat transfer area suitable for that point.

[0070] In the first embodiment, the first stage heat exchanger HEX1 has two sub-heats whose effective heat transfer areas are 1.0 times and 0.5 times that of the basic heat exchanger HEX1a, respectively. Although the example in which exchangers HEX1b and HEX1c are provided is shown, the number of sub-heat exchangers in this first-stage heat exchanger HEX1 and the ratio of their actual heat transfer area to the basic heat exchanger are determined depending on the refrigeration load R. It may be set appropriately in consideration of the optimum substantial heat transfer area in the zero operating state. For example, since the optimum point is set to a higher value of the load ratio R/L than the point E-2 shown in FIG. If the refrigeration load can reach a point of 0 (that is, the point of R/L = ∞) by multiplying by .0, the basic heat exchanger and one unit with approximately the same heat transfer area The first stage heat exchanger HEX1 may be configured with a sub-heat exchanger. This also applies to the device shown in the second embodiment.

Furthermore, the setting of the effective heat transfer area of each heat exchanger in the present invention does not have to be carried out strictly, and it is possible to have an error of the same degree as the error that generally exists in the setting of the above-mentioned effective heat transfer area. May contain.

Furthermore, in the present invention, the gas to be liquefied and frozen is not limited to helium, but other gases having a boiling point lower than nitrogen, such as hydrogen or neon, can also be used in the liquefaction refrigeration device to achieve the same effect as described above. is possible.

Based on the above reasons, the setting of the heat transfer area of the heat exchanger in the present invention can be summarized as follows.

(1) Among the plurality of expansion turbines, three heat exchangers (in accordance with the present invention The intermediate heat exchanger) is divided into two, and the substantial heat transfer area of each divided heat exchanger is set to approximately half the optimum substantial heat transfer area at the optimum point.

(2) When an expansion turbine is not provided in the high pressure line (device shown in the first embodiment),
The first stage heat exchanger (low-temperature heat exchanger according to the present invention) closest to the JT valve 10 is composed of a basic heat exchanger and one or more auxiliary heat exchangers, and the actual heat transfer area of the basic heat exchanger is is set approximately equal to the optimal effective heat transfer area at the optimal point, and
The substantial heat transfer area of the auxiliary heat exchanger is set to 0.5 to 1.0 times the substantial heat transfer area of the basic heat exchanger.

(3) When an expansion turbine is provided in the high pressure line (the device shown in the second embodiment), two
One heat exchanger (low-temperature heat exchanger according to the present invention) is composed of a basic heat exchanger and one or more auxiliary heat exchangers, and the effective heat transfer area of the basic heat exchanger is optimized at the optimum point. The area is set approximately equal to the area, and the substantial heat transfer area of the sub-heat exchanger is set to be 0.5 to 1.5 times the substantial heat transfer area of the basic heat exchanger.
Set to 0x.

[0077]

Effects of the Invention As described above, the present invention consists of three intermediate heat exchangers consisting of two heat exchangers having substantially equal heat transfer areas, and a low-temperature heat exchanger that is connected to a basic heat exchanger and one or more heat exchangers. It consists of a sub-heat exchanger and a sub-heat exchanger, and by switching the heat exchanger used in the intermediate heat exchanger and the low-temperature heat exchanger, the actual heat transfer area of each heat exchanger can be changed. Therefore, by setting these effective heat transfer areas to an effective heat transfer area suitable for operation at the desired load ratio R/L, the operating state can be adjusted only by adjusting the opening of the JT valve as in the past. Compared to equipment that undergoes changes, the range of operable load ratios R/L can be greatly expanded, and stable and highly efficient refrigeration/liquefaction operation at each point and large total liquefaction/refrigeration loads can be achieved. This has the effect of ensuring R+L. Moreover, since a single heat exchanger that does not require a change in the heat transfer area can be used as in the conventional case, it is possible to prevent the device from increasing in size.

Furthermore, by configuring the intermediate heat exchanger and low-temperature heat exchanger so that heat conduction occurs between the heat exchangers constituting the heat exchanger, it is possible to operate using one of the heat exchangers. Even if the heat exchanger is in use, the heat transfer from this heat exchanger can keep the other heat exchanger that is not in operation cool, reducing the thermal shock when switching between heat exchangers. This has the effect of making it possible to smoothly switch the operating state.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram of a helium liquefaction refrigeration apparatus in a first embodiment of the present invention.

FIG. 2 is a graph showing changes in Carnot efficiency and temperature difference between heat exchangers as the load ratio R/L changes in the above device.

FIG. 3 is an explanatory diagram showing a heat transfer structure of a fifth stage heat exchanger provided in the above device.

FIG. 4 is a flow diagram of a helium liquefaction refrigeration apparatus in a second embodiment.

FIG. 5 is a graph showing changes in Carnot efficiency as the load ratio R/L changes in the above device.

FIG. 6 is a flow diagram showing an example of a conventional helium liquefaction device.

FIG. 7 is a graph showing the limit of the load ratio R/L in the above device.

[Explanation of symbols]

10 JT valve (expansion liquefaction means) 16, 38 switching valve (switching means) 28, 29, 30, 31, 32, 33 switching valve (switching means) 48, 50, 60, 62 switching valve (switching means) C
Compressor (compression means) HEX1 to HEX10 Heat exchanger HEX1a, HEX2a Basic heat exchanger HEX1b,
HEX1c, HEX2b Secondary heat exchanger HEX3a, H
EX3b Heat exchangers HEX4a, HEX4b forming the 3rd stage heat exchanger Heat exchangers HEX5a, HEX5b forming the 4th stage heat exchanger Heat exchangers HEX6a, HEX6b forming the 5th stage heat exchanger 6th stage heat Heat exchanger 5c constituting the exchanger Heat conduction parts T1 to T5 Expansion turbine

Claims (4)

[Claims] Claim 1: Compression means for compressing a gas to be treated;
A plurality of heat exchangers arranged in series, an expansion liquefaction means that expands high pressure gas that has passed through these heat exchangers and liquefies at least a part of it, and expands a part of the gas on the high pressure side. and an expansion turbine that generates cold and sends it to the low-pressure side, the high-pressure gas compressed by the compression means is cooled by heat exchange in the plurality of heat exchangers, and is expanded to a desired proportion by the expansion and liquefaction means. In the liquefaction refrigeration apparatus configured to liquefy gas, make the remaining gas contribute to refrigeration, pass it through the heat exchanger in a low pressure state, and return it to the compression means, in the heat exchanger group, the temperature It consists of three intermediate heat exchangers sandwiching an expansion turbine whose level is below the boiling point of nitrogen and closest to the boiling point of nitrogen, and two heat exchangers that are arranged in parallel and have substantially equal heat transfer areas. At the same time, the low-temperature heat exchanger closest to the expansion liquefaction means is arranged in parallel with the basic heat exchanger, and has an effective transfer rate of 0.5 to 1.0 times that of the basic heat exchanger. A liquefaction refrigeration system comprising at least one sub-heat exchanger having a thermal area, and comprising a switching means for switching the heat exchanger used in the intermediate heat exchanger and the low-temperature heat exchanger. [Claim 2] Compression means for compressing a gas to be treated;
A plurality of heat exchangers arranged in series, an expansion liquefaction means that expands and liquefies at least a part of the high-pressure target gas that has passed through these heat exchangers, and a part of the gas on the high-pressure line side. A first expansion turbine that expands the gas to generate cold and sends it to the low-pressure side, and a second expansion turbine installed in the high-pressure line, converts the high-pressure gas compressed by the compression means into the plurality of heat sources. The gas is cooled by heat exchange in the exchanger, a desired proportion of the gas is liquefied by expansion by the expansion means, and the remaining gas is contributed to refrigeration, passed through the heat exchanger in a low pressure state, and returned to the compression means. In the liquefaction refrigeration system configured as above, among the heat exchanger group, the first
The three intermediate heat exchangers sandwiching the second expansion turbine are configured by two heat exchangers arranged in parallel with each other and having substantially equal heat transfer areas, and the two intermediate heat exchangers sandwiching the second expansion turbine. A low temperature heat exchanger is arranged in parallel with the basic heat exchanger and the basic heat exchanger.
A liquefaction refrigeration system comprising one or more sub-heat exchangers having a substantial heat transfer area of 1.0 times. 3. The liquefaction refrigeration system according to claim 1 or 2, wherein the intermediate heat exchanger is configured such that heat conduction occurs between the two heat exchangers constituting the intermediate heat exchanger. Characteristic liquefaction refrigeration equipment. 4. The liquefaction refrigeration system according to claim 1 or 2, wherein the low-temperature heat exchanger is configured such that heat conduction is performed between a basic heat exchanger and an auxiliary heat exchanger constituting the low-temperature heat exchanger. A liquefaction refrigeration device characterized by being configured as follows.